Methods of Forming Patterned Photoresist Layers Over Semiconductor Substrates

ABSTRACT

This invention comprises methods of forming patterned photoresist layers over semiconductor substrates. In one implementation, a semiconductor substrate is provided. An antireflective coating is formed over the semiconductor substrate. The antireflective coating has an outer surface. The outer surface is treated with a basic fluid. A positive photoresist is applied onto the outer surface which has been treated with the basic treating fluid. The positive photoresist is patterned and developed effective to form a patterned photoresist layer having increased footing at a base region of said layer than would otherwise occur in the absence of said treating the outer surface. Other aspects and implementations are contemplated.

RELATED PATENT DATA

This patent resulted from a continuation application of U.S. patentapplication Ser. No. 11/481,493, filed Jul. 5, 2006, entitled “Methodsof Forming Patterned Photoresist Layers Over Semiconductor Substrates”,naming Jon P. Daley as inventor, which resulted from a continuationapplication of U.S. patent application Ser. No. 10/655,997, filed Sep.5, 2003, entitled “Methods of Forming Patterned Photoresist Layers OverSemiconductor Substrates”, naming Jon P. Daley as inventor, now U.S.Pat. No. 7,115,532, the disclosures of which are incorporated byreference.

TECHNICAL FIELD

This invention relates to methods of forming patterned photoresistlayers over semiconductor substrates.

BACKGROUND OF THE INVENTION

A continuing goal in semiconductor processing is increasedminiaturization while maintaining high performance. Modern semiconductorprocesses are still heavily reliant on photolithography when fabricatingsemiconductor circuitry to achieve this goal.

Photolithography is a commonly-used method for patterning featuresduring semiconductor processing. A radiation-sensitive material (i.e.,photoresist) is formed over a substrate which is ultimately to bepatterned, for example by etching or ion implanting. The photoresist issubsequently subjected to radiation which modifies the solubility of theimpacted versus the unimpacted regions in a suitable developer solution.Accordingly, the radiation is provided in a desired pattern so that someportions of the photoresist are impacted by the radiation while otherportions of the photoresist are not impacted by the radiation. Thephotoresist is then subjected to developing conditions which selectivelyremove either the impacted or the non-impacted portions. Photoresistsare typically designed to be either negative or positive. If thephotoresist is a positive photoresist, the impacted portions areselectively removed. If the photoresist is a negative photoresist, thenon-impacted portions are selectively removed.

The photoresist remaining after development defines a patterned mask.The pattern of such mask can subsequently be transferred to theunderlying material using appropriate etching and/or implantingtechniques to form patterned features in material beneath the mask. Adifficulty which can be encountered during photolithographic processingis that the radiation utilized to pattern the photoresist can bereflected from the underlying layer or layers to cause variousconstructive and destructive interference patterns to occur. This canadversely affect the pattern ultimately developed in the photoresist.

One manner of addressing the reflective issues is to initially form anantireflective coating over the layer or layers to be patterned, andforming a layer of photoresist thereover. Further, multipleantireflective coating materials or layers might be utilized, as well asmultiple layers of resist and/or non-radiation sensitive hard masking orother layers. Various antireflective coating materials have beendeveloped. Some are principally organic in nature, while others areprincipally inorganic in nature. DARC, which stands for DepositedAntireflective Coating, is typically understood within the industry todefine inorganic antireflective coatings formed of silicon, oxygen,nitrogen and sometimes hydrogen. Another commonly used class ofantireflective coating is BARC, which stands for Bottom AntireflectiveCoating. BARC materials are principally organic in nature.

The continuing goal and effect of circuitry miniaturization hastypically resulted in greater reduction in the horizontal dimension asopposed to the vertical dimension. In the etching of features, this hasresulted in narrower yet correspondingly increasing height in thefeatures being formed, something typically referred to as increasingaspect ratio. Correspondingly, the photoresist masks utilized to formsuch features typically also have increased aspect ratios. Accordingly,adherence of the photoresist to the underlying antireflective coating orother layers takes on increasing significance towards precludingdisplacement or toppling of the masking blocks formed in the patternedphotoresist. Further and regardless, the photoresist and antireflectivecoating materials can interact, particularly during a post-exposure bakeof the photoresist prior to solvent development. For example, materialat the outer surface of the antireflective coating materials can migrateinto the photoresist, and/or the photoresist can interact with materialon the outer surface of the antireflective coating which can, one orboth, adversely affect adherence or desired control in the ultimatepattern produced in the photoresist.

In most instances, it is highly desirable that the photoresist maskingblocks which are formed have substantially vertical sidewalls from topto bottom of the photoresist layer. However, the patterned photoresistcan tend to flare out at the bottom/bases of the individual maskingblocks forming what is commonly referred to as footing. The degree offooting can be exacerbated by use of certain antireflective coatings,principally the result of interaction between the photoresist and outersurface of the antireflective coating.

While the invention was motivated in addressing the above-identifiedissues, it is in no way so limited. The invention is only limited by theaccompanying claims as literally worded, without interpretative or otherlimiting reference to the specification, and in accordance with thedoctrine of equivalents.

SUMMARY

This invention comprises methods of forming patterned photoresist layersover semiconductor substrates. In one implementation, a semiconductorsubstrate is provided. An antireflective coating is formed over thesemiconductor substrate. The antireflective coating has an outersurface. The outer surface is treated with a basic fluid. A positivephotoresist is applied onto the outer surface which has been treatedwith the basic treating fluid. The positive photoresist is patterned anddeveloped effective to form a patterned photoresist layer havingincreased footing at a base region of said layer than would otherwiseoccur in the absence of said treating the outer surface.

In one implementation, a method of forming a patterned photoresist layerover a semiconductor substrate includes providing a semiconductorsubstrate having an outer surface. The outer surface is treated with abasic fluid. Photoresist is applied onto the outer surface which hasbeen treated with the basic treating fluid. The photoresist is patternedand developed to form a patterned photoresist layer.

Other aspects and implementations are contemplated.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic, cross-sectional, fragmentary view of asemiconductor substrate in process in accordance with an aspect of theinvention.

FIG. 2 is a view of the FIG. 1 substrate fragment at a processing stepsubsequent to that shown by FIG. 1.

FIG. 3 is a view of the FIG. 2 substrate fragment at a processing stepsubsequent to that shown by FIG. 2.

FIG. 4 is a diagrammatic, cross-sectional, fragmentary view of a priorart semiconductor substrate processed in contrast to the FIG. 3substrate fragment.

FIG. 5 is a diagrammatic, cross-sectional, fragmentary view of asemiconductor substrate in process in accordance with an aspect of theinvention.

FIG. 6 is a view of the FIG. 5 substrate fragment at a processing stepsubsequent to that shown by FIG. 5.

FIG. 7 is a view of the FIG. 6 substrate fragment at a processing stepsubsequent to that shown by FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

A method of forming a patterned photoresist layer over a semiconductorsubstrate is described initially with reference to an exemplaryembodiment as depicted in FIGS. 1-3. Referring initially to FIG. 1, awafer fragment 10 comprises a semiconductor substrate 12. In the contextof this document, the term “semiconductor substrate” or “semiconductivesubstrate” is defined to mean any construction comprising semiconductivematerial, including, but not limited to, bulk semiconductive materialssuch as a semiconductive wafer (either alone or in assemblies comprisingother materials thereon), and semiconductive material layers (eitheralone or in assemblies comprising other materials). The term “substrate”refers to any supporting structure, including, but not limited to, thesemiconductive substrates described above. Further, the term “layer”encompasses the singular and the plural unless otherwise indicated.Accordingly, semiconductor substrate 12 might comprise multipledifferent materials and/or layers which may include, by way of exampleonly, bulk semiconductor materials and/or semiconductor-on-insulatorlayers.

An antireflective coating 14 is deposited over semiconductor substrate12. Antireflective coating 14 has an outer surface 16. Outer surface 16could be organic, alternately inorganic, or a combination of organic andinorganic. Exemplary inorganic materials, and by way of example only,include various DARC materials as described above. Exemplary organicmaterials include the above-described BARCs. The invention was reducedto practice utilizing DongJin A20 BARC available from the DongJinSemiconductor Company, Ltd. of Kyungki-do of South Korea. However, ofcourse, any material for outer surface 16 is contemplated, whetherexisting or yet-to-be developed.

Outer surface 16 is treated with a basic fluid exemplified by thedepicted downwardly directed arrows 17. The basic treating fluid mightbe liquid, gaseous, or a combination of liquid and gaseous. In thecontext of this document, a basic treating fluid which is “liquid” or“gaseous” constitutes at least 95% of such phase. Regardless, in onepreferred implementation, the basic treating fluid has a pH of at least8.5, and more preferably a pH of at least 10.5. By way of example only,exemplary preferred basic treating fluids include tetramethyl ammoniumhydroxide, potassium hydroxide, sodium hydroxide, ammonium fluoride, andaqueous alkylamine fluids. Specific exemplary alkyl amines includeethylamine, cyclohexylamine, and methylbutylamine. Of course, variouscombinations or mixtures of the stated, or other materials, might alsobe employed.

The treating might be conducted under room ambient temperature and roomambient pressure conditions with the basic treating fluid thereat,although temperatures and/or pressures above and/or below room ambientconditions are also of course contemplated. Accordingly, any combinationof pressure and temperature might be employed. Any time of treating canbe employed, with 2 minutes or less being one preferred example, and 1minute or less being a more preferred example. Such might be dependentupon pH, treatment pressure, treatment temperature, etc. in conjunctionwith being effective to obtain some desired objective from the treating.

Referring to FIG. 2, a positive photoresist 18 is applied onto outersurface 16 (meaning in contact therewith) which has been treated withthe basic treating fluid. An exemplary, and reduction to practicematerial was AR360 available from the Shipley Company of Marlborough,Mass. Any desired suitable thicknesses can be utilized for layers 14 and18. By way of example only, an exemplary thickness range for layer 14 isfrom 300 Angstroms to 800 Angstroms, with an exemplary thickness rangefor layer 18 being from 2000 Angstroms to 3350 Angstroms.

Referring to FIG. 3, positive photoresist 18 has been patterned anddeveloped effective to form a patterned photoresist layer 18 a. Asdepicted, layer 18 a can be considered as having a base region 20 wherethe depicted footing commences. In accordance with one aspect of theinvention, the outer surface treating with the basic fluid results inthe patterning and developing of the positive photoresist beingeffective to form the patterned photoresist layer to have increasedfooting at the base region of said layer than would otherwise occur inthe absence of treating the outer surface with a basic fluid. Forexample, FIG. 4 depicts a prior art construction identical with the FIG.3 construction and processed in accordance therewith identically but fortreating of outer surface 16 of antireflective coating 14 with a basicfluid. FIG. 3 depicts greater degree or increased footing than occurredrelative to the FIG. 4 processing.

In one preferred implementation, outer surface 16 is at least partiallydried intermediate the basic fluid treating and the application ofpositive photoresist, and even more preferably completely driedintermediate the treating and photoresist applying. Further preferablyin one preferred embodiment, outer surface 16 is not exposed to anyliquid intermediate the basic fluid treating and the application ofpositive photoresist. For example, and preferably, outer surface 16 isallowed to dry under ambient or elevated temperature conditions withoutany intervening spraying or even rinsing with deionized water over outersurface 16. Alternately but less preferred in an aspect of theinvention, the outer surface might be treated with other fluids (forexample which may be aqueous, non-aqueous, pH neutral, pH below 7,gaseous, liquid, etc.) intermediate the basic fluid treating and theapplication of photoresist. Further, outer surface 16 might be treatedmultiple discrete times with the same or different basic fluids.Regardless, treatment of a surface with a basic fluid prior tophotoresist application in accordance with the invention might be forany purpose, including for yet to-be-determined purposes, reasons orobjectives. An existing purpose might be to consume known or unknownreactants present on the surface being treated which might otherwiseadversely affect some aspect of the subsequent photoresist processing.

The invention was reduced to practice, for example, in conjunction withinventive processing depicted by FIG. 3 relative to a series of controlwafers depicted in FIG. 4. The control and inventive wafers wereidentically processed, but for treatment with a basic fluid to outersurface 16 prior to application of a photoresist layer thereover. Theantireflective coating material utilized was the DongJin A20 BARC, withthe photoresist being AR360 positive Shipley photoresist. The basicfluid utilized was liquid tetramethyl ammonium hydroxide having a pH of10.9. Such was puddled atop outer surface 16, with the basic fluid andsubstrate being at room ambient temperature and pressure conditions.After approximately 60 seconds of such treating, the substrates werespun to substantially expel the liquid from outer surface 16. Such outersurface was then allowed to completely dry in an amine scavengingambient prior to application of the Shipley A360 photoresist. Uponradiation exposure and develop, the widths of the masking blocks weremeasured at multiple elevations for determining ratios of a width at themiddle illustrated portions of the masking blocks of FIGS. 3 and 4 ascompared to the widest portions at the feet of such masking blocks. Thecontrol wafers as depicted in FIG. 4 provided an average ratio of footwidth to middle width of 1.504, whereas the substrates processed inaccordance with the invention had an average ratio of foot width tomiddle width of 2.060, thereby demonstrating increased degree offooting. Treatment with the basic fluid might enhance adhesion of thephotoresist to an antireflective coating, and/or increased footing canresult in a greater area of adhesion to an antireflective coating whichmight be significant in preventing masking blocks with large aspectratios from toppling.

The invention was principally developed and directed to the issues andsubstrate constructions for example as generally described above.However, the invention is in no way so limited and may haveapplicability in other aspects and implementations. For example,processing might occur as described above utilizing an antireflectivecoating with a basic fluid treatment and independent of whetherincreased footing occurs as compared to non-basic fluid treatedantireflective coating surfaces. Further by way of example only, theinvention is applicable to treatment of substrates which do notnecessarily have antireflective coatings, and accordingly, might even behighly reflective or transmissive of the incident radiation utilized topattern the photoresist. Regardless, by way of example only, the treatedouter surfaces might comprise silicon oxide materials, for example,boron and/or phosphorous doped silicon dioxide glasses. Alternately byway of example only, the treated outer surfaces might comprise anitride, such as silicon nitride or titanium nitride. Further, by way ofexample only, the outer surface might comprise a material such assilicon carbide which has previously been used as a hard maskingmaterial in multilayer resist systems.

Further and regardless, the invention has applicability to use withnegative photoresists in addition to positive photoresists, andregardless of use of an antireflective coating. FIGS. 5-7 depict animplementation and a method of forming a patterned photoresist layerover a semiconductor substrate in accordance with an aspect of theinvention. Referring initially to FIG. 5, a semiconductor substrate 30has an outer surface 32. Such might comprise an antireflective material,a highly reflective material, or a light transmissive material relativeto incident radiation ultimately to be utilized in fabricating aphotoresist layer. Further, semiconductor substrate 30 comprisesmaterial 34 which may constitute one or more layer or layers ofinsulative, conductive, and/or semiconductive materials which might behomogenously or non-homogenously distributed. Regardless, outer surface32 is treated with a basic fluid as depicted by downwardly directedarrows 36. The basic fluid treating is preferably in accordance with anyof the attributes described above with respect to the first embodiment,and as claimed herein.

Referring to FIG. 6, photoresist 38 has been applied onto outer surface32 which has previously been treated with the basic treating fluid.Attributes are preferably as described above, and as claimed herein.Again, reflective, antireflective, or radiation transmissive materialsmight be utilized above or below layer 38, and layer 38 might constituteone or a combination of positive and/or negative photoresists, as wellas other layers which might not be radiation sensitive.

Referring to FIG. 7, photoresist 38 has been patterned and developed toform a patterned photoresist layer 38 a. Etching of material beneathlayer 38 a, or ion implanting or other processing whether existing oryet-to-be developed, could then be conducted through openings formed inlayer 38 a.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1-52. (canceled)
 53. A method of forming a patterned photoresist layerover a semiconductor substrate, comprising: providing a semiconductorsubstrate; depositing an antireflective coating over the semiconductorsubstrate, the antireflective coating having an outer surface; treatingthe outer surface with a basic fluid, the basic treating fluid being atroom ambient temperature and room ambient pressure during the treating;applying photoresist onto the outer surface which has been treated withthe basic treating fluid; and patterning and developing the photoresistto form a patterned photoresist layer.
 54. The method of claim 53wherein the outer surface is not exposed to any liquid intermediate thetreating and the applying.
 55. The method of claim 53 wherein the outersurface is at least partially dried intermediate the treating and theapplying.
 56. The method of claim 53 wherein the outer surface iscompletely dried intermediate the treating and the applying.
 57. Themethod of claim 53 wherein, the outer surface is not exposed to anyliquid intermediate the treating and the applying; and the outer surfaceis at least partially dried intermediate the treating and the applying.58. The method of claim 57 wherein the basic treating fluid is liquid.59. The method of claim 57 wherein the outer surface is completely driedintermediate the treating and the applying.
 60. The method of claim 53wherein the outer surface is organic.
 61. The method of claim 53 whereinthe outer surface is inorganic.
 62. The method of claim 53 wherein thebasic treating fluid has a pH of at least 8.5.
 63. The method of claim53 wherein the basic treating fluid has a pH of at least 10.5.
 64. Themethod of claim 53 wherein the basic treating fluid is liquid.
 65. Themethod of claim 53 wherein the basic treating fluid is gaseous.
 66. Themethod of claim 53 wherein the basic treating fluid comprisestetramethyl ammonium hydroxide.
 67. The method of claim 53 wherein thebasic treating fluid comprises potassium hydroxide in addition to the atleast one of tetramethyl ammonium hydroxide and ammonium fluoride. 68.The method of claim 53 wherein the basic treating fluid comprises sodiumhydroxide in addition to the at least one of tetramethyl ammoniumhydroxide and ammonium fluoride.
 69. The method of claim 53 wherein thebasic treating fluid comprises ammonium fluoride.
 70. The method ofclaim 53 wherein the basic treating fluid comprises an alkyl amine inaddition to the at least one of tetramethyl ammonium hydroxide andammonium fluoride.
 72. The method of claim 53 wherein the outer surfacecomprises a silicon oxide-containing material.
 73. The method of claim53 wherein the outer surface comprises an organic-containing material.74. The method of claim 53 wherein the outer surface comprises a siliconnitride-containing material.
 75. The method of claim 53 wherein theouter surface comprises a silicon carbide-containing material.